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Check callback parameters bivariantly if they result from instantiation (#56218)

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This commit is contained in:
Anders Hejlsberg
2023-12-01 10:38:04 -08:00
committed by GitHub
parent 5bc6617738
commit 8da01f3583
7 changed files with 414 additions and 5 deletions
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src/compiler/checker.ts
+7 -2
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@@ -20691,8 +20691,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// similar to return values, callback parameters are output positions. This means that a Promise<T>,
// where T is used only in callback parameter positions, will be co-variant (as opposed to bi-variant)
// with respect to T.
const sourceSig = checkMode & SignatureCheckMode.Callback ? undefined : getSingleCallSignature(getNonNullableType(sourceType));
const targetSig = checkMode & SignatureCheckMode.Callback ? undefined : getSingleCallSignature(getNonNullableType(targetType));
const sourceSig = checkMode & SignatureCheckMode.Callback || isInstantiatedGenericParameter(source, i) ? undefined : getSingleCallSignature(getNonNullableType(sourceType));
const targetSig = checkMode & SignatureCheckMode.Callback || isInstantiatedGenericParameter(target, i) ? undefined : getSingleCallSignature(getNonNullableType(targetType));
const callbacks = sourceSig && targetSig && !getTypePredicateOfSignature(sourceSig) && !getTypePredicateOfSignature(targetSig) &&
getTypeFacts(sourceType, TypeFacts.IsUndefinedOrNull) === getTypeFacts(targetType, TypeFacts.IsUndefinedOrNull);
let related = callbacks ?
@@ -33486,6 +33486,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
(typeArguments.length >= minTypeArgumentCount && typeArguments.length <= numTypeParameters);
}
function isInstantiatedGenericParameter(signature: Signature, pos: number) {
let type;
return !!(signature.target && (type = tryGetTypeAtPosition(signature.target, pos)) && isGenericType(type));
}
// If type has a single call signature and no other members, return that signature. Otherwise, return undefined.
function getSingleCallSignature(type: Type): Signature | undefined {
return getSingleSignature(type, SignatureKind.Call, /*allowMembers*/ false);